/Engine/Source/Runtime/RenderCore/Public/RenderTargetPool.h
true if the old element was still valid, false if a new one was assigned
bool FindFreeElement ( [FRHICommandList](API\Runtime\RHI\FRHICommandList) & RHICmdList, const [FPooledRenderTargetDesc](API\Runtime\RenderCore\FPooledRenderTargetDesc) & Desc, [TRefCountPtr](API\Runtime\Core\Templates\TRefCountPtr)< [IPooledRenderTarget](API\Runtime\RenderCore\IPooledRenderTarget) > & Out, const TCHAR * InDebugName )